feat: accept unknown enum values in fromObject

[alexander-fenster]

In official protobuf implementations unknown numeric enum values are accepted and not discarded. Changing the behavior of fromObject to store unknown enum values. toObject will also dump them as is (without converting to a string, because it does not know the string representation for an unknown enum value).

I'm not changing verify which still won't accept unknown values.

Since the changes in the code generators are hard to read, here are some examples.

Imagine this proto:

syntax = "proto3";

enum E {
  DEFAULT = 0;
  KNOWN = 1;
}

message M {
  E a = 1;
  repeated E b = 2;
}

This is the diff in the generated code for fromObject and toObject, explanations are below.

--- original.js	2022-08-26 16:51:09.932392333 +0000
+++ changed.js	2022-08-26 17:23:27.797270346 +0000
@@ -3,6 +3,9 @@
   return d
   var m=new this.ctor
   switch(d.a){
+  default:
+  if(typeof(d.a)==="number"){m.a=d.a;break}
+  break
   case"DEFAULT":
   case 0:
   m.a=0
@@ -19,6 +22,7 @@
   for(var i=0;i<d.b.length;++i){
   switch(d.b[i]){
   default:
+  if(typeof(d.b[i])==="number"){m.b[i]=d.b[i];break}
   case"DEFAULT":
   case 0:
   m.b[i]=0
@@ -43,12 +47,12 @@
   d.a=o.enums===String?"DEFAULT":0
   }
   if(m.a!=null&&m.hasOwnProperty("a")){
-  d.a=o.enums===String?types[0].values[m.a]:m.a
+  d.a=o.enums===String?(types[0].values[m.a]===undefined?m.a:types[0].values[m.a]):m.a
   }
   if(m.b&&m.b.length){
   d.b=[]
   for(var j=0;j<m.b.length;++j){
-  d.b[j]=o.enums===String?types[1].values[m.b[j]]:m.b[j]
+  d.b[j]=o.enums===String?(types[1].values[m.b[j]]===undefined?m.b[j]:types[1].values[m.b[j]]):m.b[j]
   }
   }
   return d

Previously, this was the code generated for fromObject and toObject (comments added):

function M$fromObject(d){
  if(d instanceof this.ctor)
  return d
  var m=new this.ctor
  switch(d.a){      // for single enum values, there's no "default:" clause, it ignores unknown values
  case"DEFAULT":
  case 0:
  m.a=0
  break
  case"KNOWN":
  case 1:
  m.a=1
  break
  }
  if(d.b){
  if(!Array.isArray(d.b))
  throw TypeError(".M.b: array expected")
  m.b=[]
  for(var i=0;i<d.b.length;++i){
  switch(d.b[i]){
  default:
  case"DEFAULT":    // for repeated enum values, it replaces unknown values with default values
                    // to avoid having holes in array
  case 0:
  m.b[i]=0
  break
  case"KNOWN":
  case 1:
  m.b[i]=1
  break
  }
  }
  }
  return m
}
function M$toObject(m,o){
  if(!o)
  o={}
  var d={}
  if(o.arrays||o.defaults){
  d.b=[]
  }
  if(o.defaults){
  d.a=o.enums===String?"DEFAULT":0
  }
  if(m.a!=null&&m.hasOwnProperty("a")){
  d.a=o.enums===String?types[0].values[m.a]:m.a // will put undefined for unknown value
  }
  if(m.b&&m.b.length){
  d.b=[]
  for(var j=0;j<m.b.length;++j){
  d.b[j]=o.enums===String?types[1].values[m.b[j]]:m.b[j] // same here
  }
  }
  return d
}

With the changes, the following code will be produced:

function M$fromObject(d){
  if(d instanceof this.ctor)
  return d
  var m=new this.ctor
  switch(d.a){
  default:
  if(typeof(d.a)==="number"){m.a=d.a;break} // if an unknown value is a number, use it as is,
  break                                     // otherwise, ignore it since it's not an array
  case"DEFAULT":
  case 0:
  m.a=0
  break
  case"KNOWN":
  case 1:
  m.a=1
  break
  }
  if(d.b){
  if(!Array.isArray(d.b))
  throw TypeError(".M.b: array expected")
  m.b=[]
  for(var i=0;i<d.b.length;++i){
  switch(d.b[i]){
  default:
  if(typeof(d.b[i])==="number"){m.b[i]=d.b[i];break} // for arrays, use unknown numbers as is, but
  case"DEFAULT":                                     // don't leave holes
  case 0:
  m.b[i]=0
  break
  case"KNOWN":
  case 1:
  m.b[i]=1
  break
  }
  }
  }
  return m
}
function M$toObject(m,o){
  if(!o)
  o={}
  var d={}
  if(o.arrays||o.defaults){
  d.b=[]
  }
  if(o.defaults){
  d.a=o.enums===String?"DEFAULT":0
  }
  if(m.a!=null&&m.hasOwnProperty("a")){
  d.a=o.enums===String?(types[0].values[m.a]===undefined?m.a:types[0].values[m.a]):m.a
  // will put a number for unknown value
  }
  if(m.b&&m.b.length){
  d.b=[]
  for(var j=0;j<m.b.length;++j){
  d.b[j]=o.enums===String?(types[1].values[m.b[j]]===undefined?m.b[j]:types[1].values[m.b[j]]):m.b[j]
  // same here
  }
  }
  return d
}